1. Field of the Invention
The present invention relates to a method for controlling a plurality of devices in which the plurality of devices are connected to one another, and in which the devices are mutually controlled by communication between the devices.
2. Description of the Related Art
In recent years, audio video (AV) systems conforming to a standard entitled Project 50 protocol (AV-LINK) have been developed in Europe. Such AV systems have, for example, a TV receiver 1 and a video cassette recorder 2 connected to each other via a “21 PIN” connector as shown in FIG. 1. Alternatively, it is possible to construct a larger-scale AV system by having another AV device such as a DVD player provided between the TV receiver 1 and the video cassette recorder 2. With the AV system conforming to the Project 50 protocol, the transmit and receipt of commands between a plurality of AV devices control mutually the operation of the AV devices.
The AV devices including the TV receiver 1, the video cassette recorder 2 and the like have installed therein so-called OSD (on-screen display) function for multi-displaying the state of its own and the other devices and manipulation menu, etc. on a screen of the TV receiver 1, providing easy manipulation for the user.
However, the AV system conforming to the Project 50 protocol has a problem as follows, when a video signal reproduced from the video cassette recorder 2, for example, is fed to the TV receiver 1 to have the signal shown on a screen 11. When the video cassette recorder 2 makes a mode change, for example, from “STOP” to “PLAY”, the OSD function of the recorder 2 prepares a multiple video signal which multiplexes the mode change display onto reproduced image, supplying the signal to the TV receiver 1. On the other hand, the TV receiver 1 detects the mode change of the video cassette recorder 2 based on state data received from the video cassette recorder 2, allowing the OSD function of the receiver 1 to multi-display the mode change on the screen 11.
As a result, the TV receiver 1 has displayed on the screen 11 the mode display according to the OSD function of the recorder 2 and the mode display according to that of the receiver 1 as overlapped. In the case where the manufacturer of the receiver 1 is different from that of the recorder 2, for example, the two mode displays are different in timing and method due to the difference in a specification and concept between the manufacturers, entailing the problem that the screen looks disturbed, and contents displayed are hardly read when the two mode displays are overlapped at a same position.